Trailing blade coater blade loading mechanism



A ril 7, 1964 A. J. SCHMITT 3,128,207

TRAILING BLADE COATER BLADE LOADING MECHANISM Filed Sept. 7, 1961 2Sheets-Sheet 1 IN VEN TOR. /%'"?zafa Josey)? 02%? if A TTORNE YS April7, 1964 A. J. SCH MITT 3,128,207

TRAILING BLADE CQATER BLADE LOADING MECHANISM Filed Sept. 7, 1961 Q 2Sheets-Sheet 2 ATTORNYS United States Patent 3,128,207 TRAILING BLADECOATER BLADE LOADING MECHANISM Arnold Joseph Schmitt, Beloit, Wis.,assignor to Beioit Iron Works, Beloit, Wis., a corporation of WisconsinFiled Sept. 7, 1961, Ser. No. 136,636 4 Claims. (Cl. 118126) The presentinvention relates to improvements in mechanism for loading an elementwith a controlled pressure against a moving web and more particularly toa fluid pressure operated loading mechanism for holding coating elementsagainst a moving web on a coater back up roll.

The invention is used in a trailing blade coating mechanism whereincoating is applied to the surface of a moving paper Web carried on acoater back up roll and the coating is smoothed by a doctor blade heldin pressure engagement with the web. Accurate control of the pressure ofthe blade against the web is essential to control the amount of coatingapplied to the sheet. The blade, in addition to being held accuratelyagainst the web at a predetermined controlled pressure, must be movedaway from the back up roll during threading, clean up and blade changeoperations. Due to the mass of the system, sensitive loading becomesdifficult, and handling of the mechanism requires equipment sufficientto support the heavy weight as well as controllably and accurately loadthe blade against the Web.

A feature of the present invention is the provision of blade loadingmechanism which moves the blade away from the back up roll to a restposition, carries the blade up to the roll to a ready position, movesthe blade into contact with the sheet and a very light kiss contactstarting blade pressure preventing any excess of coating from passingthrough on the sheet and coating up the after driers, paper rolls and soforth, and loads the blade against the moving paper Web with apredetermined controllable sensitive operating force.

Coating may be applied to the moving web ahead of the blade by variousmeans such as by an applicator roll. The applicator roll must also bemovable relative to the back up roll to a rest position for threadingand clean up, and be movable into coating contact with the web with acontrollable application pressure.

A feature of the invention is the provision of a loading mechanism whichcan be used on an applicator roll of a paper coating machine capable ofmoving the applicator roll to a rest position away from the back up rollor to a ready position adjacent the back up roll, and to coating contactwith the moving paper web with an accurately controlled nip pressurebetween the rolls.

An object of the present invention is to provide an improved loadingmechanism for holding coating elements against a moving paper web with asensitively controlled loading pressure, and which is capable of movingthe elements away from the roll to a rest position. It will berecognized from the description of the mechanism that while certainadvantages are obtained in use with paper coating mechanism, andparticular advantages are obtained in certain arrangements withdifferent elements of the paper coating mechanism, the features of theinvention may also be employed for loading other elements of papermachines, and may be used for example in loading rolls of printingmachinery.

A further object of the invention is to provide an improved loadingmechanism for a trailing blade coater wherein a first loading devicesupports the dead weight of the mechanism and a second loading deviceoperates to apply and control the loading pressure of the blade againstthe moving web.

A still further object of the invention is to provide a ICC loadingmechanism capable of accurately positioning the trailing blade of acoating mechanism against a moving web with a starting blade pressureload at a very light predetermined plate pressure that prevents anexcess of coating from passing through the sheet and prevents tearing ofthe fibers from the sheet and excessive heating of the blade and whichalso compensates for the static load of the assembly, and is capable ofapplying an operating blade pressure over a relatively wide range ofaccurately and sensitively controlled pressures.

One of the problems of operating trailing blade coaters, particularly athigh speeds, is involved in loading the blade against the dry sheetinitially before the coating is applied to the sheet. The initial dryrunning tends to tear fibers from the sheet that become lodged under theblade and cause streaks. It also causes the blade to heat up, burn andwarp.

One of the objects of the invention is to provide an improved loadingmechanism which accurately and sensitively controls starting bladepressures eliminating the problems which heretofore existed.

During running coating operation, there is a definite relationshipbetween the coater Weight applied to the sheet and the trailing bladepressure. With increasing blade pressure the coating weights decrease.With sensitive operating blade pressure control, coating weights can bemore precisely controlled. Coating pressures have been controlled invarious ways such as by providing adjustable mechanical stops.

An object of the present invention is to provide an improved mechanismfor sensitively controlling the operating coating blade pressureavoiding difliculties heretofore encountered, and wherein bladepressures can be readily changed from day to day operation or duringshifts, or at any time during operation by simple adjustment of airpressure.

Other objects and advantages and features will become more apparent withthe teaching of the principles of the invention in connection with thedisclosure of the preferred embodiment thereof in the specification,claims and drawings, in which:

FIGURE 1 is a schematic end elevational view showing a trailing bladecoater in accordance with the present invention;

FIGURE 2 is a schematic detailed end elevational view of a blade holdingmechanism; and

FIGURE 3 is a schematic end elevational view of an applicator rollconstructed in accordance with the present invention.

As shown on the drawings:

FIGURES l and 2 show a coater back up roll 10 with a paper web W carrierthereon. A doctor blade 11 is shown in operating position against theweb smoothing coating applied by suitable means, such as by spraying,rolling or by a bath, and an applicator roll is shown at 23 and itsassociated mechanism will be described in detail in connection with theillustration of FIGURE 3.

As shown in FIGURES l and 2, the mechanism for holding and positioningthe doctor blade 11 includes a first pivotal arm 12 pivotally supportedon a rigidly mounted bracket 13, and a second pivotal arm 14 pivotallymounted on a rigidly supported bracket 15. Between the arms is connecteda fluid pressure operated positioning means in the form of a cylinder 16with a piston therein connected to a piston rod 17. The piston rod ispivotally connected at 19 to the second or the upper arm 14, and thepiston travels within the cylinder 16 by controlling the flow of airinto the cylinder through air lines 16a and 16b.

When pressurized air is admitted to the lower line 16a the piston willtravel to the top of the cylinder against a stop, not shown, to bringthe blade 11 up to a ready position. In this position the blade 11 willbe a small distance on the order of /2 from the web W when pneumaticloading units 21 and 22 are not pressurized.

When the lower end of the cylinder 16 is vented through line 16a, theWeight of the arm 14 will cause it to drop downwardly to a rest positionwhere the blade 1s away from the back up roll. In this positionoperations of threading, clean up and blade changing can be performed.

When the arm 14 and blade 11 are moved up to the ready position, thepneumatic unit 21 is pressurized by opening a valve 21a in a lineleading to the interior of the unit The units 21 and 22 are closedpneumatic cells having annular outer flexible walls so that they expandwhen pressurized. This type of unit is frequently referred to as an airspring. Air is admitted to the unit 21 at a predetermined pressure whichis related to the characteristic of the unit 21 so that the blade 11 isbrought ust up into contact pressure with the web- W, with the pneumaticunit 21 supporting the dead weight of the arms 12 and 14 and theelements supported thereon. This is the starting and operating positionof the blade, and the unit 21 applies a force to bring the blade intocontact with the web W with a starting pressure. This is a very lightpredetermined blade pressure that prevents any excess of coating frompassing through the coating mecha- I11SI11 on the sheet and therebyprevents any coating up of the after driers, paper rolls, etc.

The starting blade pressure is also light enough to prevent tearing ofthe fibers from the sheet and to prevent excess of heating of the bladethat might damage it prematurely. The pressure for providing thisstarting force is obtained by a pressure regulator 21b in the lineleading to the loading unit 21.

When coating is applied to the web W for regular operation, the unit 22applies an operating force to load the blade 11 against the web with anoperating pressure. Air pressure is supplied to the unit 22 by opening avalve 2% in the line leading to the unit, and the pressure in the unitis controlled by a variable pressure regulating valve 22a. The operatingblade pressure is therefore controlled by varying the air pressure inthe loading unit 22 and control is sensitively obtainable over arelatively wide range of air pressures. The sensitivity is possiblebecause the load unit 22 controls only the blade pressure, and load unit21 has compensated for the dead weight or mass of the system. Valve 21bfor the unit 21 is normally preset for the weight of the elements, and22a is regulated in accordance with the operating pressure desired. Bothunits 21 and 22 have small travel and can be more accurate inasmuch asthe long travel is provided by the cylinder 16. As will be appreciated,there are a number of control systems that can be provided with the useof interlocks to properly sequence and automate the loading operationsfor supplying air pressure to the cylinder 16, and the loading units 21and 22.

FIGURE 2 illustrates a blade clamping device which may be employed,wherein a pivotal blade clamp 24 is supported in a socket 24a in the arm14. The clamp is urged against the blade 11 to hold it against a seatingsurface 25 by a toggle linkage including links 26 and 26a. Link 26a ispivoted to the clamp 24, and link 26 is pivoted on a bracket on the arm14, and the links are pivotally connected to each other at 27. Theclamping position of the toggle linkage is limited by an adjustable stop28 on the arm 14, and the toggle linkage is held in its clampingposition by an expansible rod 29 which incorporates a micrometer formeasuring the length of the rod so as to accurately control the clampingpressure. The micrometer has a rounded base end 31 for being pivotallysupported in a seat on a bracket on the arm 14. For releasing the bladethe micrometer rod 27 is contracted and slipped out vfrom underneath thepivotal 4 connection 27, so that the linkage can pivot downwardly andrelease the blade 11.

FIGURE 3 illustrates the applicator roll 33 which carries coating up tothe paper web W, receiving coating on its surface in a container 33a.

The applicator roll 33 is rotatably mounted and is supported on a rollsupport 34 which is mounted on a pair of pivotally supported parallellinks 35 and 36 which are connected at their base ends to a fixedsupport 37. The coating container 33a is carried on the roll support 34to move with the roll 33. A positioning means in the form of an aircylinder 38 with a piston therein connected to a piston rod 39 moves thesupport 34 between a rest position, wherein the applicator roll ispositioned away from the backing roll 33, and a ready position, whereinthe applicator roll is positioned close to the back up roll. Thecylinder 38 is provided with suitable air lines, not shown, and when thebase of the cylinder is pressurized, the support 34 swings up on thelinks 35 and 36 against a stop pin 40 which is adjustably threaded intoa fixed bracket 41 for determining the rest position.

The applicator roll 33 is rotatably supported in a hearing 42 on an arm43 which is pivotally mounted at 43a on the support 34. A loading unit45 expands to load the applicator roll against the web W on the back uproll 32.

The loading unit is in the form of a closed expansible chamber having aflexible outer jacket and is of the type of unit which is known as anair spring. The loading unit is mounted on a bracket 44 on the support34, and an air line connects to the interior of a loading unit 45. Acontrol valve 46 is opened to admit air to the unit 45, and acontrollable pressure regulating valve 47 regulates the pressuresupplied to the unit 45. By varying the air pressure in the unit 45, theloading pressure of the applicator roll 33 can be accurately controlled.

In operation, air is released from the cylinder 38 to permit theapplicator roll to be dropped away from the back up roll to a restposition, which may be as far as 6" to 8" from the back up roll. Tobring the applicator roll 33 up to ready position, air is admitted tothe cylinder 38 until the support 34 strikes the adjustable stop 40. Atthis position there is a gap of /s" to 4" between the rolls 32 and 33,and thus the cylinder 38 has provided a support for the weight of themechanism to bring the roll 33 to operating position. The gap is closedby ad mitting air under pressure to the unit 45 pivoting the arm 43upwardly and bringing the applicator roll to operating position with anoperating pressure dependent upon the regulation of the valve 47. Thispermits accurately controlling the nip pressure between the rolls 32 and33. A more accurate nip pressure is obtainable inasmuch as the cylinder38 takes care of the unavoidable dead weight of the mechanism.

It is contemplated that the mechanism may be employed with a sheet breakdetector which operates when a break is detected in the web W, anddisconnects the air supply to the cylinder 38 so that air will beimmediately released with a break in the web causing the roll 33 to dropaway from the back up roll 32. The air in the line to the loading unit45 may be connected to the same source so that this unit will collapsewith breakage of the web W. The tray or pan 33a is conveniently mountedon the support 34 so that it will drop away with the support and movewith the roll 33. The parallel linkage 35 and 36 will maintain the tray33a in its horizontal position so that the coating therein will not bespilled.

Thus it will be seen that I have provided an improved coating mechanismwhich meets the objectives and advantages before set forth and whichavoids disadvantages heretofore present.

The drawings and specification present a detailed disclosure of thepreferred embodiments of the invention, and it is to be understood thatthe invention is not limited to the specific forms disclosed, but coversall modifications, changes and alternative constructions and methodsfalling within the scope of the principles taught by the invention.

I claim as my invention:

1. In a paper coating machine the combination comprising means forapplying a layer of coating to a moving paper web, a trailing coatingblade for applying the coating to the web surface, a starting fluidpressure means supporting the weight of the blade and moving the bladeinto touching contact with the web at a light predetermined pressurepreventing an excess of coating on the sheet from passing the blade, acontrol fluid pressure means applying a predetermined variable operatingpressure to said blade solely to control operating pressure forobtaining sensitive pressure control, a first pivoted arm connected tosaid starting and said control fluid pressure means with said startingmeans and control means connected in parallel, a second pivotal armconnected to said blade, and a positioning fluid pressure means betweensaid arms for transmitting the forces of said first and second pressuremeans to said blade and for moving the blade from a rest position awayfrom the web to a ready position adjacent the Web.

2. In a paper coating machine, the combination comprising, means forapplyin a layer of coating to a moving paper web, a trailing coatingblade for applying coating to the web surface, a first pivotal arm, asecond pivotal arm supporting said blade for movement from a restposition away from the web to a coating position in closerunningrelationship to the web surface, a piston and cylinder connected betweensaid first and second arms for moving said second arm to carry the bladebetween said rest position and coating position, a first fluid operatedmeans connected to said first arm, and a second fluid operated meansconnected to said first arm parallel to said first means so that saidfirst and second means both apply a force to said blade through saidfirst and second arms.

3. In a paper coating machine, the combination comprising, means forapplying a layer of coating to a moving paper web, a trailing coatingblade for applying coating to the web surface, a first pivotal arm, asecond pivotal arm supporting said blade for movement from a restposition away from the web to a coating position in closerunningrelationship to the web surface with said second arm extendingsubstantially horizontally in said coating position, a piston andcylinder connected substantially horizontally of the pivotal point ofsaid first arm between said first and second arms for moving said secondarm to carry the blade between said rest and coating positions, saidfirst arm having a downwardly extending portion, a first fluid operatedmeans connected to said downwardly extending portion, and a second fluidoperated means connected to said downwardly extending portion parallelto said first means so that said first and second means both apply aforce to said blade through said first and second arms, said first meansapplying a force substantially equal to the weight of said arms andblade with the piston and cylinder, and said second means applying avariable operating force to control the force between said blade and thesurface of the web.

4, In a paper coating machine, the combination comprising, a coatingapplying member movable between a coating position in close-runningrelation to a web surface and a rest position, a shiftable carrierincluding pivotally mounted parallel links and including a bar pivotallyconnected to said links, an adjustable stop engaged by said carrier in aready position with said applying member in close-running relation tothe web surface, a piston and cylinder connected to said carrier movingthe carrier between positions to move the applying member from said restposition to said coating position, a pivotal arm mounted on said barcarrying said applying member, and a fluid pressure operated memberbetween said bar and said arm controlling the operating pressure betweenthe web and said applying member.

References Cited in the file of this patent UNITED STATES PATENTS1,031,620 Callan July 2, 1912 2,534,320 Taylor Dec. 19, 1950 2,566,811Stevenson Sept. 4, 1951 2,568,446 Griffin Sept. 18, 1951 2,589,966 RulloMar. 18, 1952 2,861,541 Hornbostel Nov. 25, 1958 3,026,796 Crawford Mar.27, 1962 FOREIGN PATENTS 213,765 Australia Mar. 20, 1958 741,970 GreatBritain Dec. 14, 1955 751,549 Great Britain June 27, 1956 869,939 GreatBritain June 7, 1961

1. IN A PAPER COATING MACHINE THE COMBINATION COMPRISING MEANS FORAPPLYING A LAYER OF COATING TO A MOVING PAPER WEB, A TRAILING COATINGBLADE FOR APPLYING THE COATING TO THE WEB SURFACE, A STARTING FLUIDPRESSURE MEANS SUPPORTING THE WEIGHT OF THE BLADE AND MOVING THE BLADEINTO TOUCHING CONTACT WITH THE WEB AT A LIGHT PREDETERMINED PRESSUREPREVENTING AN EXCESS OF COATING ON THE SHEET FROM PASSING THE BLADE, ACONTROL FLUID PRESSURE MEANS APPLYING A PREDETERMINED VARIABLE OPERATINGPRESSURE TO SAID BLADE SOLELY TO CONTROL OPERATING PRESSURE FOROBTAINING SENSITIVE PRESSURE CONTROL, A FIRST PIVOTED ARM CONNECTED TOSAID STARTING AND SAID CONTROL FLUID PRESSURE MEANS WITH SAID STARTINGMEANS AND CONTROL MEANS CONNECTED IN PARALLEL, A SECOND PIVOTAL ARMCONNECTED TO SAID BLADE, AND A POSITIONING FLUID PRESSURE MEANS BETWEENSAID ARMS FOR TRANSMITTING THE FORCES OF SAID FIRST AND SECOND PRESSUREMEANS TO SAID BLADE AND FOR MOVING THE BLADE FROM A REST POSITION AWAYFROM THE WEB TO A READY POSITION ADJACENT THE WEB.